In JP-A 60-100516, a sustained-release microcapsule of a water-soluble drug, which comprises a particle of an average diameter of 2 to 200 μm containing a water-soluble drug dispersed in a matrix comprising a lactic acid-glycolic acid copolymer having weight average molecular weight of about 5000 to 200000 and comprising about 100 to 50% by weight of lactic acid and about 0 to 50% by weight of glycolic acid, and which is prepared by a method of drying in water is disclosed.
In JP-A 62-201816, a sustained-release microcapsule characterized in that the viscosity of a W/O type emulsion upon preparation of a W/O/W type emulsion is adjusted to about 150 to 10000 cp, and a process for preparing the same are disclosed.
In JP-A 62-54760, there are disclosed a biodegradable polyoxycarboxylic ester which is a copolymer or a polymer having the content of water-soluble oxycarboxylic acid of less than 0.01 mole/100 g in terms of a monobasic acid and having a weight average molecular weight of about 2000 to 50000, and an injection sustained-release microcapsule containing the polymer.
In JP-A 61-28521, there are disclosed a lactic acid-glycolic acid copolymer which has weight average molecular weight of about 5000 to 30000, does not contain a catalyst, has the dispersibility (by a gel permeation chromatography method) of about 1.5 to 2 and comprises about 50 to 95% by weight of lactic acid and 50 to 5% by weight of glycolic acid, and a pharmaceutical containing the polymer as a base.
In JP-A 6-192068, there is disclosed a process for preparing a sustained-release microcapsule, which comprises heating a microcapsule at a temperature higher than the glass transition temperature of a polymer, at which respective particles of the microcapsule do not adhere to each other.
In JP-A 4-218528, there is disclosed a method for purifying biodegradable aliphatic polyester, which comprises dissolving a biodegradable aliphatic polyester containing a low-molecular weight polymer having a molecular weight of 1,000 or smaller in an organic solvent, adding water thereto to precipitate a polymeric substance, and removing low-molecular weight polymer having molecular weight of 1,000, and there is described that water is added at 50 to 150 (ratio by volume) relative to 100 of the organic solvent.